This invention relates to shell and tube heat exchangers and, more particularly, to a heat exchanger having an improved tube and shell configuration and a method making such a heat exchanger.
In heat exchangers, employing tubes for carrying heating or cooling fluids, it is known that the tubes can be configured in various patterns or configurations. See, for example, U.S. Pat. Nos. 5,044,431 and 4,357,991. As shown or disclosed therein, the heat exchange tubes are configured in circular or elliptical patterns, with certain spacing requirements between the tubes being specified. In the '991 patent, the tubes extend vertically of a shell and are arranged in a concentric pattern. In the '431 patent, the tubes also extend vertically of a shell but are either arranged in a generally elliptical pattern, or in a square or rectangular pattern with each side of the square or rectangle concavely curving. In each instance, the tube arrangement is to facilitate compact tube packing while maintaining uniform fluid flow through the individual tubes.
It is known that in a heat exchanger, the fluid flows into the heat exchanger at one point, is directed through the tube arrangement both by placement of the tubes themselves, as well as by baffles, for example, and then exits the heat exchanger at a second location. To maximize heat transfer, not only is the tube arrangement as discussed in the above referenced patents important, but so are matters such as uniform flow paths, the prevention of acoustical noise, resonance or vibration, the physical size of heat exchanger required for the particular tasks, etc. While the various tube configurations shown and described in these patents try to address some of these problems, it will be noted with respect to the above referenced patents, that there are still non-uniform flow paths (for example, at the corners of the various tube layouts of the '431 patent) which result in some of the problems discussed above. On the other hand, some heat exchangers built in accordance with the '991 patent are known to generate acoustical noise. Other arrangements are, however, possible by which not only-is more efficient heat transfer achieved, but in which these other problems are solved.
In addition to the aforementioned, another significant factor in these prior heat exchangers is their cost. One problem attendant with some earlier heat exchangers is that due to their size, they could only be manufactured on site. Fabricating the exchanger in a shop (where fabrication costs are much lower), transporting the unit to the site, and installing it there is preferable.